ADAM 20 and 21; two novel human testis-specific membrane metalloproteases with similarity to fertilin-alpha.
Two novel membrane disintegrin-metalloproteases, ADAM 20 and ADAM 21 were cloned from a human testis cDNA library. Their predicted translation products share 50% sequence identity with each other. Among previously characterized ADAMs, the best similarity was to sperm cell-specific fertilins-alpha and -beta, and meltrin-gamma (ADAM 9) which is ubiquitously expressed. Both ADAM 20 and 21 mRNAs are exclusively expressed in testis, presumably, in analogy to all other testis-specific ADAMs, on mature spermatocytes. Both cDNAs were mapped on the genome, and found to be tightly linked to the same marker (SHGC-36001) on chromosome 14q24.1. This region is not syntenic with the loci of mouse sperm-specific ADAMs 1-5. ADAM 20, but not 21, encodes a consensus Zn2+ binding site of active adamalysin metzincin metalloproteases, and both 20 and 21 encode putative cell-fusion peptides, required for sperm-egg fusion. Based on these characteristics it is possible that ADAM 20 and/or 21 is the functional equivalent of sperm fertilin-alpha, as it was recently reported that this gene is non-functional in humans.
Hooft van Huijsduijnen
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Geneva Biomedical Research Institute, 14 Chemin des Aulx, Case Postale 674, 1228 Plan-les-Ouates, Geneva, Switzerland. Rob.hooft@serono.com
D051722:ADAM Proteins; D000595:Amino Acid Sequence; D001483:Base Sequence; D002459:Cell Fusion; D002874:Chromosome Mapping; D002883:Chromosomes, Human, Pair 14; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000737:chemistry; D019483:Disintegrins / Q000737:chemistry / Q000235:genetics; D000072196:Fertilins; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics*; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D008666:Metalloendopeptidases / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D013737:Testis / Q000201:enzymology*
D019483:Disintegrins; D005819:Genetic Markers; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D051722:ADAM Proteins; C110998:ADAM20 protein, human; C110999:ADAM21 protein, human; C000606455:Adam1a protein, mouse; D000072196:Fertilins; D008666:Metalloendopeptidases